(04-28-2016, 11:48 AM)jproffer Wrote: mainly I'll use it for thermal/stress simulations, and probably a bunch of folding@home projects in its downtime
Ok, unfortunately it's already too late but maybe this helps others to improve their cluster setups: We did already extensive research on performance related topics. If you've an hour please read through https://github.com/longsleep/build-pine6...-191984162 where most if not all problems are outlined.
- You won't be able to get decent performance without both heatsinks and some amount of airflow (otherwise throttling will jump in and decrease performance drastically)
- Using Micro USB to power the boards is insufficient, you better use the Euler connector (this is especially necessary if you improved heat dissipation and managed to prevent throttling since using optimized code you're able to exceed the Micro USB limitations -- max. 1.8A by design and most likely undervoltage problems way earlier)
- If you're after high performance you need active cooling. By controlling the airflow and upright orientation of the boards you could use one or two large (and therefore silent) 120mm fans to increase the amount of air flowing over the heatsink's surfaces (I tested this with a few Allwinner H3 boards a while ago using flexible cardboard stripes between the boards to maximize speed of airflow over SoC/heatsink)
- If you don't like fans but want to improve performance tweaking cpufreq/dvfs settings might help: Pine64 is able to use dynamic voltage frequency scaling and by testing all your boards you might be able to decrease VDD_CPUX for the relevant dvfs operating points. Less voltage --> less temperatures --> higher clockspeeds if throttling is an issue. Also adding more cpufreq steps in the range where throttling happens might increase achievable performance by a few percent
References: http://linux-sunxi.org/Hardware_Reliability_Tests#CPU and the misused Github 'issue' above
